Positive, non-interfering signaling system



April 5, 1938. R M, HOPKINS Y 2,113,140

7 POSITIVE, NONINTERFERING SIGNALING SYSTEM Filed Aug. 17, 1952- 2 Sheets-Sheet 2 Patented Apr. 5, 1938 UNITED STATES PATENT OFFICE POSITIVE, NON-INTERFERING SIGNALING SYSTEM Application August 1'7, 1932, Serial No. 629,119

17 Claims.

This invention relates to electric signal transmission and alarm systems, and to non-interfering systems, and more particularly to systems of this kind wherein substantially simultaneously initiated signals will be automatically successively transmitted, though it is noted that in some of the claims the invention is not limited to electric transmitters.

One object of the invention is to provide an efiicient system of this kind in which a large number of transmitting stations may be operated with only two line-loops, one for transmission and one for signal initiation.

Another object of the invention is to provide a system of this kind in which both loops will be fully and separately supervised and controlled for grounds and other line defects by .a circuit and control means similar to the McCulloh system. Another object of the invention is to provide a system of this kind having control switches for McCulloh operation similar to those shown in the United States patent application of Richard Hopkins and Herbert M. Laford, Serial No. 539,316, filed May 22nd, 1931.

The inventive features for the accomplishment of these and other objects are shown herein in connection with an improved positive noninterfering successive alarm system which, briefly stated, includes a recording signal receiver, a supervisory trip control and a grounded main current source, and supervised transmitter and trip loops passing through the transmitters and connected to said source for operating the re,- ceiver and said control.

Each transmitter includes a pair of trip magnets in the trip loop, an armature adapted to be attracted by either magnet, when sufiiciently energized, to release the transmitter. Water-flowoperated detectors or other signal initiating means are connected with the transmitters respectively, and when operated, direct current from the trip loop through one magnet to the ground, thereby to operate the transmitter.

A retarding resistance interposed in the tripcircuit prevents the passage of enough current for action of the trip magnets until the resistance is removed, .as by a retarded relaymeans actuated by said trip circuit after a period longer than water hammer impulses. Also a non-inter- -ierence means operated by the transmitter circuit during signaling, operates the relay for interposing said resistance to prevent signalmixing.

{[n the accompanying drawings, Fig. 1 is a diagram of the system; and

Fig. 2 is a diagram showin-gthe transmitter and detector connections.

The principal features of the invention will first be very briefly indicated, after which the: features will be described in detail.

The system as a whole The system comprises, briefly stated, a recording signal receiver II, a supervisory trip control I2, and a grounded main current source I4, hav- 10 ing its ungrounded terminal connected to supervised transmitter and trip-loops 9 and 6 passing through the transmitters I8a, I819, I811. for operating the receiver and said control.

Each transmitter includes a pair of trip magnets 29, 29a (Fig. 2) in series in the trip loop 6, and also .a grounded signal wheel 2|, 2. normally closed switch 22, 23, 24 in the transmitter loop 9 and normally out of contact with the wheel ZI. An armature 34 is adapted to be at tracted by either magnet, when sufiiciently energized, to release the transmitter.

There is shown, by way of example, a waterflow detector associated with each transmitter, comprising means 41, 48, BI, 52, normally shunting the magnets, and operative for directing current from said loop 9 through one magnet to the ground, thereby to operate the transmitter. There are also means 60, GI, 62, 63 (Fig. 2), 'to shunt around the magnets and remove the ground after the signal is completed, to permit otherv transmitters to operate immediately.

Said signal receiver II includes McCulloh type control means 88, 88a, 88g, for adjusting the receiver to meet operating conditions forline defects in the transmitter loop- 9, and connecting the in-leg of the transmitter loop, through conductor I III, to the source during abnormal operation.

The supervisory trip-control includes, in the trip loop 6, an in-leg relay I300 comprising a normally attracted armature I361; connected to said source, and normally engaging a normally engaged contact I38a, for controlling a retarding means including a retarding resistance I40 tarded means I43, I59, I41, actuated by said trip armature I3Iia, the retarded means being sunficiently retarded to prevent the shunting out said resistance I40 unless the detector is operated longer than the usual water hammer inpulse.

A non-interference means I64, I65, operated by the transmitter circuit during transmitting, causes the retarded means I43, I59 to interpose said resistance I40 in the trip circuit, to prevent other transmitters from operating at the same time.

A control means I98, I98a, I 98g, of the Mo- Culloh type, serves for adjusting the control I2, in accordance with defects in the trip loop and. serves when adjusted to abnormal operation, to open a switch I59, I5I, for disconnecting the retarding means I43, I40 from the trip circuit relay, and to connect the in-leg terminal I34 of the trip loop 6 through conductors 220, I3 to the ungrounded terminal I6 of the said source for McCulloh operation.

The supervised Zine loops This invention is shown in combination with line loop 5, 6, I, and 8, 9, ID; a receiving station including a receiver II, I2, and a main current source I4 having grounded and ungrounded terminals I5, I6; said line including any convenient numberof transmitters I8a, I8b, I8n and associated transmitter and trip loops 6 and 9 passing through each station, each loop having its legs extending to said station, one leg 5, 8 of each being connected to said main source I4, and the other leg I; I adapted to be grounded or connected-to said mainsource, as will be explained.

The transmitters Each transmitter I8 includes a series connected pair of trip magnets 20, 20a interposed in the tripper loop 6, a grounded rotary toothed code-signal wheel 2|, and a normally closed switch 22, 23, 24, interposed in the transmitter loop 9 and normally out of contact with the wheel 2|, and having a pen 24 adapted tobe engaged by the teeth of the wheel 2| when rotating, thereby once for each tooth, to ground 4 both legs 8, I0 of the loop 6 and also to break the loop.

The transmitter includes a normally wound clockwork 26, comprising a winding arbor 2! having a squared end, and a clock spring anchored thereto, and a gear train having pawl and ratchet connection with saidarbor, thereby to be driven in one direction only by said spring, and comprising a signal wheel shaft 32, carrying said grounded toothed signal wheel 2|, and a cam 33. An armature 34, adapted to be raised by either of said magnets when operatively energized, carries a pin 35, forming means for engaging a projection 36 of said clockwork for holding the clockworkagainst operation when the armature is unattracted, and releasing it when the armature is. attracted. A cam 38 on said winding arbor has a notch 39 therein and an extended land portion 48, and is adapted to engage a connecting bar 4I secured to said armature and normally engaged in said notch 39 when the armature is retracted, and engaged by said land portion when. the arbor is unwinding to hold the armature in attracted transmitter-releasing position, to prevent the transmitter from stopping until the signal is completed.

Signal initiating means Signal initiating means such as a water flow detector 43, 44 for a pipe 45 includes a pivoted member 43, 44, carrying a fan 44, and having an outwardly projecting arm 43, carrying an insulator block 45', operating a normally closed shunt switch 41, 48 connected by conductors 49, 58in shunt around said pair-of tripper magnets 20, 20a, and a normally open ground switch 52 adapted when the detector is operatedto connect a ground 53, through conductors 54, 55, and switch members 62, 63, with the loop portion 56 between said magnets 28, 20a, whereby said detector 43, 44 operates to open the shunt switch 41, 48, and to connect said portion 56 to the ground 53, the portion of the trip circuit most remote from the source I4 is shunted out, and current passes from said source through one magnet 20, or 20a, to the ground, and if of suflicient strength, attracts the armature 34 and allows the transmitter to send a code-signal to the receiver II.

Loop restorer A switch assembly 60, 6|, 62, 63 on said transmitter includes a normally open shunt switch 60, 6|, shunted around said magnets 20, 28a, and a normally closed switch 62, 63 in series with said ground switch 5|, 52, members 68, 63 being connected by aninsulating piece 44. Said cam has a notch 64 normally to receive the pen-end 65 of member 60, and a raised portion 66 adapted to engage said pen after the signal has been initiated and completed, thereby to close the switch BI, 62, thereby shunting around the magnets 20, 29a, and to open the switch 62, 63, thereby removing the ground to allow the passage of current through loop 6 for the operation of other transmitters.

Parts 61, 68 and 69 of Fig. 2 symbolize stop means for the winding arbor and cam 38. When the transmitter runs'down the stop projection 68 engages the stop pin 69 and stops the transmitter with the armature raised and the notch 64 about the position of the dotted lines. When the arbor is rewound, the projection 68 strikes and stops against the pin 61, with the notch 39 not registering with the bar 4|, whereby the projection 35 is held raised until the transmitter runs down enough to bring the notch to the position of the dotted lines and .the recess 39 under the bar to lower the projection 35 and stop the transmitter in the position shown.

I The code signal recording receiver The receiving and supervising station II, I2 includes a code-signal receiver I for said transmitter loop 8; 9, ID. The receiver I I comprises an out re1ay I0 and an in relay a respectively including magnets II, Ila between and in series with which the transmitter loop 8, 9, I0 is connected, the magnets II being connected by conductor I3 to the terminal I6 of the main source of current, the other terminal 72 of the in-magnets being normally grounded, as will be explained, whereby the circuit is closed and supervised, and being at other times connected to said ungrounded source terminal I6.

The respective transmitter relays I8, 18a comprise also normally attracted armatures I6, I60, carrying or constituting a movable switch element connected by conductors I1, 13 with the source I4, and respectively engageable with normally engaged contacts I8, 18a, normally constantly engaged by said elements during normally closed circuit, when no signal is being sent, and intermittently engaged during signal sending during open circuit operation in the adjacent leg 8 or ID of the loop. The relays also respectively include normally constantly disengaged contacts 88, 88a intermittently engaged for signal sending during normal closed circuit operation, and constantly engaged, when no signal is sent; during open circuit condition in the M cC'uZloh-type adjusting means Control means for connecting said lamp and recorder to the proper contacts of said relays to meet operating conditions for defects in the transmitter loop, now to be described, comprises an out-signal switch 80, an in-signal switch 88a, and a ground switch 889, each switch comprising a substantially semi-circular series or bank of contacts, including a contact N for normal operation, a contact G for grounded closed circuit operation, a contact GO vfor operation with grounded out-leg of an open circuit, a contact for open circuit without loop ground, and a contact 0G grounded in-leg of an open circuit. A rotatable shaft 89, coaxial with all of said banks, carries insulated contact arms 90, 90a, 9091, for said banks, respectively, the arms being fast on said shaft, and simultaneously engageable respectively with corresponding associated bank contacts, as the shaft is rotated by means of an operating knob 9I, fast on said shaft, or in any other suitable manner.

Conductors 93, 94, respectively connect the ungrounded terminals of said recorder and lamp to the contact arms 90, 90a; and a normally open switch 95, 96 connects, by conductors 93, 94, 91, said ungrounded lamp and recorder terminals except when closed during abnormal operation, by a cam 98, 99, fast on said shaft.. Said cam is shown with a-notch 98 receiving the end of the switch member 95 to allow the switch to open during normal operation, and a land portion 99 for engaging the member 95 and closing the switch when the arms are adapted for abnormal operation, which requires that the recorder be able to operate from both relays.

Conductors I00 connect the normal operation contact N, the grounded closed-circuit operation contact G and the grounded out-leg open circuit contact GO of the out-signal switch 88 with the normally disengaged contact 80, to permit normal signal operation by code signal current through the out-relay when one of said contacts is engaged by the associated contact arm 90, and to permit the supplying to the recorder a current of longer duration should damage to the transmitter loop cause the armature of the outrelay to come to rest on the normally disengaged contact 80, and to cause said pilot lamp to light. This happens when the contact arms are on contacts G or G0, the switch 95, 90 being then closed.

Conductors IOI connect the open circuit contact and the grounded out-leg contacts 0 and 0G of switch 88 to the normally engaged contact I8, whereby when the condition of damage to the line requires the armature to rest on the normally disengaged contact 80, the arm 90 will be engaged with one of said contacts 0 or 0G, and signals to be recorded may be received from the normally engaged contact 18, and current of longer duration caused by change of such line condition, will cause the in-relay armature 18 to rest a longer time on the normally engaged contact to cause the lamp to indicate that the operator should move the contact arm 90 from the engaged bank contact.

Conductors I04 connect the normal operation contact N and contacts G and 0G of the insignal switch 88a with the normally disengaged contact 80a, to transmit code-signal impulses to the recorder when one of such contacts is engaged by the contact arm 90a, and to permit sup'r plying, to the pilot lamp, a current of longer duration to indicate that the arms should be re-, volved, should change in the line condition cause the armature to come to rest on the normally disengaged contact 80a.

Conductors I05 connect the open circuit contact GO and thegrounde-d out leg open circuit contact 0 to the normally engaged contact 18a, whereby when the condition of damage to the line requires the armature to rest on the normally disengaged contact 80a, current for signals to be recorded may be received from the normally engaged contact, and current of longer duration caused by change of such line condition,will cause the pilot lamp to indicate that the contact arm should be moved from such contact.

A conductor I0I connects the terminal I4 of the in-magnet Ila to the contact arm 90g of the ground switch 880, the latter contact being connected by a conductor I08 to a ground I09, for

closed-circuit normal operation of the system; while conductors IIO, I3 connect the other ground switch bank contacts G, GO, 0 and 0G to the ungrounded terminal I6 of said source, whereby when abnormal line loop condition requires the current to pass out through the inmagnet, the latter will be connected to the source.

Supervisory trz l-control The supervisory trip control I2 for said trip loop serves, as will be explainedfor controlling the retarding of the tripping impulses in the loop 6, in case of water hammer, and for adjusting the tripper loop in case of line defect, by means similar to the relays I0 and switches 88. Said trip control includes an out relay I30 and in relay I 30a, respectively including magnets I3I, I3Ia between and in series with which the trip loop 5, 6, I is connected, the main-source ungrounded terminal I6 being connected by conductors I3, I33 to the out-magnet, the other terminal I34 of the in-magnet being normally grounded, whereby thev circuit is normally closed and supervised, and being at other times connected to said ungrounded source terminal I6, as will be explained.

Each trip-control relay I30, I300; comprises a normally attracted armature I36, I3Ba, carrying or comprising a movable switch element connected by conductors 13, I31 to said source I4, and a normally engaged contact I38, I38a normally constantly engaged by said movable ele- The retarding me'ans A retarding resistance I40 is interposed in the trip circuit I3, I33, 5, 6, I, between thecurrent source I6 and the control. I2, whereby normally sufiicient current for supervising the trip circuit is allowed to pass, but not enough for operating the trip magnets 20, 20a; and said retarding means serves for shunting out said resistance when the detector is operated a time longer than the usual water hammer impulse. fAretarding relay I42, I43 has one end of its coil connected to a ground I 45, and the other connected by conductors I46, I41, I48 and a normally closed switch I50, I5I, with the normally engaged contact I38a of the tripper circuit in-relay I30a, whereby the retarding relay is normally energized, thereby attractingsaid retarding relay armature I42, and normally disconnecting from its contact I 53, connected by conductor I54 to the conductor I33 between the resistance I40 and magnet I3I. This holds the resistance I40 unshunted.

When the operation of detector switch 41, 48, 5I, 52 short circuits the magnet I 3Ia and drops the armature I36a, the circuit through conductors 13, I31, I36a, I38a, I48, I41, I46, magnet I43 and ground I 45 is broken, and the magnet I43 would release its armature I42 immediately and short circuit the resistance I40, and thereby increase the strength of the trip loop current immediately, were it notfor retarding means now to be described.

This retarding means includes a double-throw switch I55, I56, I51 having one fixed contact I55 connected by conductor I46 to the ungrounded terminal of the retarding magnet I 43. A condenser I59, having one plate grounded, has the other connected by a conductor I60 to the movable element I56'of said double-throw switch, whereby said condenser may be normally connected to said retarding magnet I43, whereby when said retarding relay magnet is energized, the condenser will be charged, and when the trip-circuit in-relay armature I36 drops and disconnects the retarding magnet from the source,

1 the condenser I59 discharges through the magnet I43 and holds the same energized a short time, thereby delaying the release of the armature I42 a few seconds, so as to prevent release by water hammer actuation of the detector 43, 44.

After the condenser has discharged, the armature I42 is released and engages said contact I53, thereby to shunt around said retarding resistance I40 and allow the passage of sufficient current for the operation by the trip magnet whose associated "detector 43, 44 has been operated.

Interference-preventing means An interference-preventing relay I64, I65 having its magnet coil I64 interposed in the conductor 11 of the transmitter circuit between the out-relay 10 and source I4, also has its armature I65 connected to the source, through conductors 11, 13. A contact I66 is engaged by the armature when normally attracted, and is connected by a conductor I61, I60, to the condenser I59, thereby during signaling to charge the condenser and energize the retarding magnet E43 during and between signal impulses, thereby deshunting said current-reducing resistance I40, thereby interposing the resistance and reducing the trip circuit current, thereby preventing other transmitted armatures from being raised to release with other transmitters.

Retard cut-out means When the system is used where there is no water hammer, and where it is not desired that the initiation of transmission be retarded, the movable element I56 is moved from contact I55 to contact I51, thus preventing the charging of the condenser from the conductor I41.

It is still desirable, though, that the condenser discharge in a way to energize the magnet I43 to hold the resistance'interposed during transmission, to prevent other transmitters from starting, as above explained.

To this end there is provided a retard cut-out relay I69, I10, having its armature I69 connected by conductor 13 to the current source, and one end of its magnet coil I10 connected to a ground I M and the other connected to the fixed contact I51 of said double-throw switch, whereby when the movable element of the double-throw switch is on said last named fixed contact, said condenser will not discharge through the retarding relay magnet I43, thus allowing full current to pass to the trip circuit as soon as the tripcircuit in-relay armature falls thereby.

'However, a contact I13, engaged by the armature of said cut-out relay when attracted is connected by conductor I46 to the ungrounded terminal of the retarding relay magnet coil I43, whereby during transmission the condenser I59 becomes charged from contact I66 and discharges through the cut-out relay magnet I10 to attract the cut-out relay armature I69, thereby to connect the retarding relay magnet I43 to the source and thereby break the shunt around the retarding resistance I40, thereby to weaken the trip circuit current and prevent sufficient energization of a trip magnet of another transmitter for operation thereof, thus preventing mixing of the signals.

Trip-100p defect adjusting means The relays I30, I30a constitute part of a control means for adjusting the supervisory trip control I2 for line defects. The trip-circuitrelays respectively also include normally constantly disengaged contacts I90, I900. adapted to be engaged, when a detector is operated during normal closed circuit operation, and constantly engaged, when no transmitter is operated, during open circuit condition in the adjacent leg 5 or 1. A pilot lamp I94 for the trip receiver, having one ungrounded and one grounded terminal, is lighted from said relays by a control means for connecting said lamp to the proper contacts of said trip-relays to meet operating conditions for defects in the trip loop, as will now be explained. Said control means comprises an out switch I98, and an in-switch I98a, and a ground switch I98g, each switch comprising a substantially semi-circular bank of contacts N, G, GO, 0, G, a rotatable shaft I99 and insulated contact arms200, 200a,, 2009, and an operating knob 20I, as explained of switches 88, 88a, 88g. Conductors'202 connect the ungrounded terminal of said lamp to both contact arms 200, 200a; and a cam 203 on said shaft serves for opening said normally closed switch I50, II, except during normal closed circuit operation.

Conductors 2I0 connect the operation contacts, N, G, GO of the out-switch I98 with the normally disengaged contact I00, allowing normal short pilot-lamp operation as by water hammer, and normal trip signal operation current (accompanied by code-signal current in the code companied by code-signal) that the operator should advance the contact arms until the lamp is darkened.

Conductors 2 connect the open-circuit contact O and the grounded out-leg open-circuit contact 0G of the switch I98 to the normally engaged contact I38, whereby when the condition of damage to the line requires the armature when idle to rest on the normally disengaged contact I90, indicator tripping indications may be received by the pilot lamp from the normally engaged contact, and whereby current of longer duration caused by change of such condition, will cause the in-relay armature I36 to rest on the normally engaged contact to cause the pilot lamp to light up for longer time to indicate (if unaccompanied by code-signals in the recorder) that the operator should move the contact arm 200 from the engaged bank contact and adjust the switch until the lamp becomes darkened.

Conductors 2I4 connect contacts N, G, 0G of the switch I98a with the normally disengaged contact I90a, to cause the pilot lamp to light during indicator tripping if one of such contacts is engaged by a contact arm 200a, and to cause the supply to the pilot lamp of a current of longer duration (when unaccompanied by codesignal) to" indicate that the arm should be revolved. Conductors I48, 2I5 connect contacts GO and O of the switch IBM to the normally engaged contact I38a, whereby when the condition of the line requires the armature to rest idle on the normally disengaged contact I90a, current indicating indicator tripping may be received by the lamp from the normally engaged contact I38a, and current of long duration, unaccompanied by code signal and caused by change of line location, will cause the pilot lamp to indicate that the contact arm should be moved from such bank contact.

A conductor 2I1 connects the in-magnet terminal I34 to the contact arm 209g of the ground switch; and a conductor 2I8 connects the normal operation contact N of the ground switch to a ground, for normal closed-circuit operation. Conductors 220 connect the remainder of the ground switch bank contacts G, GO, 0, 0G to the ungrounded terminal I6 of said current source, whereby when abnormal line loop condition requires that the current pass out through the in-magnet I3I, the arm 200g will be shifted to one of contacts G, GO, 0, 0G, and the inmagnet will be connected thus by conductors 2 I 1, 220 to the current source.

Normal retarded trip loop operation In normal idle condition, the transmitters and indicators are all as shown in Fig. 2 and at IBn of Fig. 1; and current passes through the trip loop 6, by way of terminal I6, conductor 13, resistance I49, conductors I33, magnets I3I, leg 5, loop 6, all switches 41, 48, leg 1, magnet I3Ia, conductors I34, 2I1, arm 200g, conductor 2I8, to ground, thus supervising the trip loop and switches 41, 48, short circuiting the magnets 20, 20a through switches 41, 43, and holding raised the relay armature I36a, to cause current to find a path through terminal I6, conductors 13, I31, armature I35a, conductor I48, switch I50, I5I, conductors I41, I46, magnet coil I43, and ground I45, thus holding the retard armature I42 away from the contact I53, thus maintaining the resistance I40 interposed in the supervised trip circuit.

As magnets 20, 20a are thus short-circuited and de-energized, the armature 34 is in lower position, and the transmitter is held against operation,

The transmitter loop 9 is also supervised, current passing through terminal I6, conductor 13, magnet 1|, leg 8, loop 9, all switches 22, 23, 24, leg I0, magnet 1Ia, conductor I01, arm 9017, conductor I08, to ground I09.

An alarm will be initiated by flow in any pipe 45, and cause the fan 44 to rise. This will open switch 41, 48 (Fig. 2) and close the switch 5I, 52, as at I8b (Fig. 1), directing current from the loop-part nearest the source through the magnet 20, switches 63, 62 and 52, 5I, to ground 53, thus energizing magnet 20, but, because of the resistance I40 in the circuit, not sufiiciently to attract the armature 34 (Fig. 2).

This operation short circuits the leg 1, through the ground 53, thus de-energizing magnet I3Ia, dropping relay armature I36a, disconnecting the magnet I43 from the armature I36a, and therefore from the current source.

Trip: operation retarding When said disconnecting takes place, the armature I42 is not released immediately because the condenser, which was charged, through conductors I60, I41, I48, will discharge through conductor I46 and magnet I43, thus holding the armature longer than a water hammer impulse.

If the detector movement was caused by water hammer, the switches 41, 48, 5|, 52 will return to normal before the condenser completely discharges and releases the armature I42; but if the detector movement was caused by sprinklerhead operation, the detector switches will remain as at I8b until the condenser discharges, whereupon the armature I42 will be released, engaging contact I53, shunting current around resistance I40 through contact I53, thus allowing full current to pass through the magnet 20 and switch 5|, 52, energizing the magnet 20 sutficiently to attract its armature and release the transmitter.

Whenever any detector switch, for instance of station I8a, is operated, current passes between grounds 53 and I5, thus short-circuiting out stations I81), I8n, more remote from the source, so that their magnets cannot be energized to release the transmitter until the loop is restored to normal, as will be explained.

Normal transmission operation The transmitter switches 22, 23, 24, are normally closed, and current normally passes from the main source I4 through magnets H, the switches 22, 23, 24, magnets 1Ia, the conductor I01, the switch arms 90g, conductor I08, to ground, and then to the grounded terminal I5 of the battery I 4. Thus the circuit is a closed super-' vised circuit. When the armature 34 (Fig. 2) is raised, the wheel 2| of that transmitter rotates and opens the switch 22, 23, 24, sending code signal in accordance with the teeth of that wheel. This intermittently breaks the circuit, intermittently closing the circuit through the source I4, conductors 13, 11, magnet I64, elements 16, 15a, conductors I00, I05, contacts N, arms 90, 90a, conductors 93, 94, to the recording receiver 85, and pilot lamp 84, respectively, to ground, thus recording the signal.

At this time the switch 95, 96 is open, for a purpose later to be explained. It will be noted that the wheel 2| is grounded but normally does not touch the spring pen member 24 of the switch 22, 23, 24.

During normal signal transmission, current passes between the signal wheel ground and ground I5, thus shorting-out the magnet IIa, allowing its armature to drop once for each tooth. At the same time the armature I6 is similarly dropped, but the leg 8 is not short circuited. Because of the capacity of the legs, and the fact that leg I0 is discharged and recharged, while the leg 8 is not, the armature 16a, in high speed Work,.1ags somewhat, and gets out of step with the armature I6. This would cause impulses from one armature, say 16a, to reach the recorder .between the impulses from the other armature I6, thus rendering the record illegible. Therefore, the switch 98, 99 is provided to separate these currents during normal operation.

When the normal intermittent signal current is sent to the .recorder through the contact N of switch 88, intermittent current also passes through contact N of switch 880,, thus flashing the lamp 84, but while the arms are on contacts N, the switch 95, 96 is open, and no current can pass from the lamp circuit to the recorder.

Under certain conditions, it might happen that the detector 43, 44 or other initiating means will, during a signal, restore to normal continuously, or one or more times. This would interrupt the signal; and such interruption is prevented by the land portion 40 (Fig. 2) of the cam 38, which moves under the bar 4|, and holds the armature raised, releasing position, until the signal is completed and until the arbor is rewound to bring the recess 39 again under the bar.

Interference preventing As soon as signaling commences, intermittent current passes through magnet coil I64, as above explained. This attracts armature I65, thus connecting the condenser, through conductors I60, I61, I3 to the source, thereby charging the condenser I59 and causing it to discharge through conductors I60, I56, I46, and magnet coil I43, thus attracting the armature I42 and interposing the resistance I40 in the trip circuit, thus preventing the passage, through the trip circuit, of current strong enough to operate any trip magnet, thus preventing the release of any other transmitter until after the signaling transmitter has finished its signal.

This prevents a second station from cutting in, whether it be nearer the source I4, or other wise cut out or not.

Restoring the transmitter loop As soon as the transmitter starts unwinding, the land portion 66 (Fig. 2) of the insulated cam 33, depresses the pen B5 of the switch member 60, thus closing the switch 60, 6| (as at I 8a of Fig. 1) and short circuiting the magnets 20, 20a. This also opens the switch 62, 63 (as at I 8a), thus entirely removingthe ground 53, and closing theloop 6, ready for the-next signal if, or asv soon as, the resistance I40 is shunted out.

Successive operation Whenthe-transmitter runs down, the notch 64 will not quite have reached the-pen B5, thus'leaving the pen depressed, the ground switch 62, 63 open and the ground out out, and leaving the switch 60, 6I' closed, thus entirely cutting out the magnets 20, 20a until they are restored to the position shown, as explained above.

Adjusting for closed-circuit grounded transmitter loop With the parts as shown in Fig. 1, suppose a ground as at 224G should occur. Current would pass direct from the ground 224G to the ground come into contact with the contacts G of all of the bank switches. This operation also rotates the cam 98, 99 closing the switch 95, 96.

If when the elements I6, 16a, dropped to the contacts 80, 80a, the attendant had failed to rotate the shaft 89, the pilot lamp would have remained lighted, calling attention to the failure of the operator.

Closed-circuit grounded transmitter-loop operation 1 a As soon as the arms have been as above noted moved to contacts G, current may pass from the source, through conductors I3, IIO, contact G of switch 889, arm g, conductor I0'I, magnet IIa, leg I0, to the ground 224G, thus raising armature 16a. At the same time current passes from source I4, through the magnet I0 and leg 8, to ground 224G, thus raising armature I6.

Now if a wheel 2I on either side of the ground 224G be rotated in sending the signal, the circuit through the adjacent leg 8 or I0 and magnet 1| or Ila will be broken, the armature I6 or 16a will be intermittently dropped, and signal current will pass intermittently through conductors I00 or I04, arm 90 or 90a, conductor 93, or conductors 94, 91, switch 95, 96, conductor 93, to the recorder 85, and asignal will be recorded at the recorder.

If the'signal is sent from the signal box I8 to the left of the ground 224G, the left hand magnet II will be operated, and viceversa.

Restoring apparatus after transmitter loop repair While the arms 90 are thus resting on contacts G, repair men should be sent to repair the line. As soon as the loop is restored to normal, no current will pass, since both ends of the loop are still connected to the terminal I6, and there is no connection with the ground I09. This will cause the dropping of both armatures I6, 16a, so that continuous current will pass through conductors I00 and I04, said arms and pilot lamp in any abnormal position of the arms indicating to the attendant to revolve the arms forwardly from these positions until the arms again engage the normal contacts N.

The operation of restoring the apparatus from any line position to normal, after repair, is included in the preceding paragraph, and need not be repeated hereinafter.

. Ground-open transmitter-loop operation Should'it happen that the circuit operating as shown in Fig. 1 should develop both a ground 224G and an open 225, the right hand magnet 1Ia. would be deenergized, the right hand armature 16a would drop. This would cause continuous current to find a path through conductors 13, 11, I04, arms 90, conductor 94, and pilot lamp, indicating that the attendant should move the arm from contacts N at least to contact G; but contact G of switch 88a is charged by conductor I04, from the dropped armature, thus lighting the pilot lamp, causing the attendant to revolve the arm to contact GO.

In this position, a closed circuit is formed through the leg 8 and ground 224G, so that the armature 16 remains raised, preventing the passage of current therefrom to conductor I00 and the pilot lamp and recorder; but if a station I8a or I81), to the left of the ground-open 224G, 225, be operated, the leg 8 will be intermittently broken, the armature 16 will be intermittently dropped, and intermittent current will pass through conductors I00, 93, and the recorder will operate.

In this condition, no current can pass the magnets 1Ia because of the open 225. This causes the armature 16a to drop away from contact 18a, thus preventing current from armature 16a from reaching the pilot lamp, thus indicating that the attendant should allow the arms to remain on contacts GO. But the leg I0 is charged; and when a station I8n is operated current passes through conductor IIO, arm 90g, conductors I01 and I0, and the ground of station I8n, thus intermittently raising the armature 16a, sendin intermittent current through conductor I05, arm 88a, conductors 91, 93, and the recorder.

Open-transmitter-loop operation If when the parts are as in Fig. 1, there should occur an accidental break in the'line as at 225, the circuit through the loop 8, 9, I0, would be broken, magnets H and 1Ia would be deenergized, armatures 16 and 16a would drop, close the circuit through conductor I04, and arm 90a, and light up the pilot lamp, warning the attendant to move the switch arms from the position N, at least as far as the intermediate contacts G and GO. As no current can pass the open, and therefore the magnets 1 I 1Ia, the armatures must stay down, and current must pass through conductors I00 and I04, and at least through one arm 90 or SM, until contact 0 is reached, whereupon the lamp would darken, as neither contact 0 is connected to an upper contact 18 or 18a.

In this position, the leg 8 is still connected to the main source; and the leg I0 is connected through magnet 1Ia, conductor I01, arm 90g, conductors H0, 13, to the source. Thus both legs and both sides of the open M will be charged, and if either transmitter I8a or Hit), or in, be operated, current would pass from the source, through one of the magnets H or 1 Ia, to a switch 22, 23, 24. The tooth of the wheel 2| touches the switch member 24 before it opens the switch, and current would pass through the toothed wheel 2 I, the ground of the station, the ground I5, to the source I4. This would cause the armatures 16, 16a, to intermittently rise, and the signal current would pass through conductors IOI or I05, arms 90 or 90a, and thence to the recorder. Thus it is seen that the circuit could operate even with an open, as at 225.

Open-grounded transmitter-loop operation Suppose the parts are as is Fig. 1, and a break 225 and a ground 226G should develop. When this happens, no current can pass through the open 225 to the magnet 1Ia, and the armature 1B and 16a would drop from the position of Fig. 1 into contact with the contact a, thus causing continuous current to pass through conductor I04, arm a, and conductor 94, to pilot lamp. This will cause the attendant to move the bank switch arms across successive contacts G, GO and 0; but at any of these positions there is always at least one contact connected to a lower contact 80 or 80a; and the attendant would at last move the arms to contacts 0G.

In this position with the arms on contacts 0G, the armature 16 is down, because no current passes the open 225; but the armature 16a is up, because current passes through conductors H0, arm fllia conductor I01, magnet 1Ia, leg I0, and ground 226G. Then if a signal be sent from station IBa, current passes through the magnet 1I, leg- 8, and the ground of station IBw, thus intermittently raising the armature 19, sending current through conductors IOI, contact 06, arm 90, conductor 93, to the recorder. If station I8n be operated, the circuit in leg I0 is thereby broken, armature 16w intermittently drops, and intermittent current passes through conductors I04, arm 90a, conductors 91, 93 and the recorder.

Adjusting from one to another abnormal transmitter-loop condition Should the apparatus be set for any abnormal condition, such as a grounded closed circuit, and then the line condition change to a condition corresponding to any subsequent switch arm position in a clockwise direction, such as an openground position, the switch arms would obviously be moved forward from the first abnormal position to the subsequent position, just as if the first abnormal condition had not existed. Thus this operation requires no further explanation.

If, however, an abnormal condition such as open-ground, having a later switch position, as at the contact 0G, should become changed to a condition corresponding to a. preceding switch position, such as the position at contacts G, GO or O, the apparatus would take care of this operation also.

Suppose, for instance, that there be the openground condition, with the circuit broken at 225 and grounded at 226G, switch arms on contacts 0G, and the armature 16 down, and the armature 160, up. Then if the break-225 should close, and there be left only the ground, current would pass through the magnet 1|, the armature 15 would rise, andcurrent would pass through conductor IOI, contact 0G, arm 99, conductors 93, 91, 94 to the pilot lamp, and the attendant would move the arm forwardly.

For every operating position, the arms 90, 90a are connected to one uncharged associated relay contact, and every line change changes the position of at least one armature, charging a previously uncharged relay contact, causing the pilot lamp to light until the arms are moved around to their proper position.

In every operating position as above described, no current passes the conductor 11 and magnet coil I64 except during signaling.

Adjustments for trip-loop defects Normal retarded trip-loop operation was described above. The trip-loop is also subject to line defect in a manner similar to that of the transmitter loop, entirely independently of the transmitter loop, as either: or both loops may have similar or different defects, or no defect, at the same time. Adjustments for defects in the different loops are entirely independent.

In all abnormal trip loop adjustments the switch I50, II is opened by a cam 203, thus deenergizing magnet I43 and cutting out the retarding resistance I40; but in all cases the trip loop will operate to send signals until proper repairs are made.

Adjustment for closed-circuit grounded trip loop With the parts as shown in Fig. 1, suppose a ground as at 229G should occur. Current would pass direct from the ground 229G to the ground I5, thus short-circuiting the line leg I and magnets I3Ia, deenergizing the magnet I3Ia, dropping the armature I36a, causing continuous current to pass from the source I6, through conductors 13, I31, armature I36a, conductor 214, contact N, arm 200a, conductor 202, through pilot lamp I 94, to ground, thus lighting the pilot lamp. If this is unaccompanied by code signal, the attendant rotates the knob I until the arms come into contact with contacts G of all the switches I98, 198a, I 98g, thus also opening the switch I50, I5I by the action of the cam 203. If the pilot lamp I94 lights up for only a short time and is followed by code signal at the recorder 85, the attendant knows that the shaft I09 and the switch arms should not be adjusted.

Closed-circuit grounded trip-loop operation As soon as the arms have been as above noted moved to contacts G, current may pass from the source I4, through conductors I3, 220, contact G of switch I98g, arm 200g, conductor 2", magnet I3Ia, leg I, to ground 220G, thus raising armature I36a. At the same time, since the switch I50, I5I is open, and armature I42 released, current passes from source I4, through conductors I3, I44, armature I42, conductors I54, I33, magnet I3I, leg 5, to ground 229G, thus supervising both legs 5 and 1, raising armature I35, and darkening the lamp, since both armatures I36, I3Ba have been raised.

Now if a detector 43, 44 on either side of the ground 229G, be actuated, a magnet 20 or 201; will be energized and release the transmitter as in normal operation.

If the signal is sent from the signal box IBa or I8b to the left of the ground 229G, the left hand magnet 20 will be energized, and vice versa.

After the repair man removes the ground 229G, no current will pass, since both ends of the loop are connected to the terminal I6, and the bank switches I98, I98a:, I981) will be restored to normal, as described of the transmitter loop.

The operation of restoring the control apparatus I2 from any position to normal after repair, will be understood from the preceding descriptions, and need not be repeated.

Ground-open trip-loop operation Should it happen that the circuit operating as shown in Fig. 1 should develop both a, ground 229G and an open 230, the right hand magnet I 3Ia would be deenergized, and the right hand armature I360, would drop. This would cause continuous current (unaccompanied by codesignal) to find a path through conductors I3, I31, 2M, arm 200a, conductors 202, causing the lamp I94 to light up, indicating to the attendant to rotate the -arm200a to contact GO. During this movement the arm 200g passes the contact G of switch I08g, and reaches contact GO, and in both cases the magnet I 3Ia is connected to,

the main source through conductor 2II, arm 2009, and conductors 220, 13; but no current passes because of the open at 230, and the armature I36a remains lowered.

In this position, a closed circuit is formed through the leg 5 and ground 220G; and if a detector of station I8a or I8b, to the left of the ground-open 229G, 230, be operated, current will pass through the magnet 20, and attract and release the transmitter. At the same time, the tripping current will merely pass between the ground 53 of the detector switch and the ground I5, so there will be no change at the armature I 36. As the open exists at 230 there will be no change at the armature I36a.

In this condition, no current can pass the magnets I 3| a because of the open 230, but the leg I is charged; and when the detector of a station I8n is. operated current passes through the magnet 20a, and the ground 53 of that station, thus raising the armature 34 and releasing the transmitter.

When this takes place, current will pass through magnet I 3| a, and lamp I94; but as this will be accompanied by code signal at the recorder 85, the attendant will not adjust the arms 200a, 2001).

Adjustments for other trip-loop defects- From the above, it is seen that the tripping magnets 20, 20a may be operated from either leg 5 or I when the leg is. either charged or uncharged, and that these adjustments for trip loop defects caused by any combination of grounds 229G or '23IG and'open 230, are similar to corresponding adjustments for transmitter loop defects, and need not be further described.

Retard-cut-oqtt operation Any abnormal position of switches I08, I 98a opens the switch I50, I5I and cuts out the retarding resistance I40 so that any magnet 20, 20a may be actuated; but repair men are sent out as soon as possible.

The operation with the retarding resistance I40 cut-out allows the trip magnets to operate as soon as the signal initiating means 43 (Fig. 2) is operated.

The apparatus is also adjusted to cut-out this trip-retard (when the retarding effect is not need ed) by moving the switch element I5'6 (Fig. 1) to engage the fixed element I51. This operation will be understood by reading the description of the retard cut-out means as given hereinbefore.

But in any case, operation of a transmitter and relay I64 causes the resistance I 40 to be interposed.

The invention claimed is:

1. In combination, a closed circuit including a trip loop; transmitters through which the loop passes, each including a trip magnet adapted to release the transmitter from normal rest posi tions when sufiiciently energized; signal initiating means for each transmitter for directing current from the trip-loop through the trip magnet of such transmitter; and retarded means operated by the trip circuit during signal initiating for increasing the current in thetrip circuit after a delay after the current is directed through the trip magnet.

2. In combination, a closed circuit including a trip loop; transmitters through which the loop passes, each including a trip magnet adapted to release the transmitter when sufliciently energized; signal initiating means, subject to water hammer, for each transmitter for directing current from the trip loop through the trip magnet of such transmitter; a reducing means associated with the circuit for reducing the current in the trip circuit, to prevent release of the transmitter; and retarded means operated by the trip circuit during signal initiating for disabling the reducing means after a delay after the current is directed through the trip magnet, said delay being long enough to avoid water hammer operation.

3. In combination, a closed circuit including a trip loop; transmitters through which the loop passes, each including a trip magnet adapted to release the transmitter when sufiiciently energized; signal initiating means for each transmitter for directing current from the trip loop through the trip magnet of such transmitter; a resistance interposed in the circuit, for reducing the current in the trip circuit, to prevent release of the transmitter; and retarded means operated by the trip circuit during signal initiating for removing the resistance, after a delay after the current is directed through the trip magnet for increasing the current in the trip circuit sufficient for releasing operation.

4. A system comprising a trip circuit; a transmitter, including a trip magnet adapted to re lease the transmitter when suficiently energized; signal initiating means constructed and con nected for directing current from the trip-circuit through the trip magnet and to short-circuit part of the trip circuit; reducing resistance in the trip-circuit, for preventing the action of the trip magnets; a retarding relay means, tending to shunt out said resistance, and actuated by said trip circuit, for preventing the shunting-out until the trip circuit is short-circuited; a condenser charged from said trip circuit and discharging through the magnet coil of said relay; 2. noninterference means operated by the transmitter during signaling, for charging said condenser.

5. A system comprising a trip circuit; a transmitter circuit; transmitters in said circuits each including a trip magnet adapted to release the transmitter when sufficiently energized; initiating means for directing current from the trip- 'circuit through the trip magnet; a resistance in the trip-circuit, for preventing the action of the trip magnets; a retarding relay means, including means for shunting out said resistance, and controlled by said trip circuit, for preventing the shunting out said resistance; a condenser charged from said trip circuit, and discharging through the magnet coil of said relay.

6. In combination, a line comprising transmitters adapted for McCulloh operation; a signal receiver including a grounded source connected to the out-leg of said line, and an out relay and in relay in the out-leg and in-leg respectively; each relay comprising an armature connected to the source, a normally engaged contact normally engageable by said armature, and a normally disengaged contact; control means including an in-switch and an out-switch for said relays respectively, each switch including a movable arm and contacts for connecting said arms to the proper contacts of said relays, to

meet operating conditions for defects in they transmitter loop; a recorder connected to the arms of the switches and means for disconnecting the in-switch arm from the recorder during normal operation.

'7. In combination, a signal receiver, including a current source having a grounded and an ungrounded terminal; a line connected to the ungrounded terminal and comprising transmitters, each including a grounded signal wheel, a nor- ,mally closed switch in the transmitter loop normally out of contact with the wheel; means to release the transmitter; said signal receiver including an out relay and in relay in the outleg and in-leg respectively; each relay comprising an armature connected to the source, a normally engaged contact normally engageable by said armature and a normally disengaged contact; control means including an in-switch for the in-relay and out-switch for each relay, the out-switch including a movable arm and contacts for connecting said arms to the proper contacts of said relays to meet operating conditions for defects in the transmitter loop; a recorder and a pilot lamp connected to the arms of the outswitch and in-switch respectively; said control means connecting the in-relay magnet to the ground during closed-circuit normal operation, and to the ungrounded terminal during abnormal operation; and means controlled by the control means for electrically connecting said arms in any operative condition except during normal operation.

8. In combination, a current source having a grounded and ungrounded terminal, a trip loop connected to the ungrounded terminal of the source; transmitters, each transmitter including a pair of trip magnets in the trip loo-p, an armature adapted to be attracted by either magnet to release the transmitter; a detector comp-rising means for directing current from said source through one magnet to the ground to operate the transmitter; a supervisory trip-control, including, in the trip-loop, an in-relay, comprising a normally attracted trip-armature connected to said source, and a normally engaged contact engageable by said armature; retarding means in the trip-circuit for preventing the action of the trip magnets, and controlled by said trip armature, for preventing the retarding means from retarding unless the detector is operated longer than a predetermined length of time; control means for adjusting the loop and trip receiver in accordance with defects in the trip loop; and means operated by the control means when adjusted to abnormal operation, for preventing the retarding means from preventing trip-magnet action.

9. In combination, a current source having a grounded and an ungrounded terminal; a trip loop connected to the ungrounded terminal; transmitters in the trip loop, each set in opera: tion with current from either direction; a detector comprising means for directing current from said loop through the transmitter to a ground to operate the transmitter; a trip-control including, in the trip loop, an in-relay; retarding means in the trip circuit for preventing the action of the transmitters, and controlled by said relay; control means for connecting the loop inleg to a ground or the ungrounded terminal and adjusting the trip control, in accordance with defects in the trip loop; and means for disconnecting the retarding means during abnormal operation. V

10. In combination, a current source having a grounded and an ungrounded terminal; a trip loop connected to the ungrounded terminal; transmitters in the trip loop, each operated with current from either direction; a detector, comprising means for directing current from said loop through the transmitter to a ground, to operate the transmitter; a trip-control, including, in the trip loop, an in-relay, comprising a normally attracted trip-armature connected to said soiu'ce, and a normally engaged contact engageab-le by said armature; retarding means in the trip-circuit for preventing the action of the transmitters and controlled current from said contact; control means for adjusting the trip control in accordance with defects in the trip loop, and connecting the in-leg of the loop to the ground during normal operation, and to the ungrounded terminal during abnormal operation; and means operated by the control means for disconnecting the retarding means from said contact during abnormal operation.

11. In combination, a grounded current source; code-signal-impulse transmitters each having a ground; a trip-loop passing through the transmitters and having one end connected to said source and the other end grounded; means separate from the trip loop for transmitting code signals from the transmitters; each transmitter including a trip magnet in the trip loop, and an armature adapted to be attracted by the magnet to start the transmitter; a signal initiating means for each transmitter normally shunting the magnet and adapted to break the shunt and direct current from the trip loop through one magnet to the transmitter ground to start the transmitter and short circuit the trip magnets of more remote transmitters to prevent the more remote transmitters from initiating signals while the less remote transmitters are transmitting; means actuated by the transmitter at the beginning of transmission for removing its ground and short circuiting its trip magnets during and after transmission and after the transmitter comes to rest.

12. In combination, a grounded current source; code-signal-impulse transmitters each having a ground; a trip-loop passing through the trans mitters and having one end connected to said source and the other end grounded; means separate from the trip loop for transmitting code signals from the transmitters; each transmitter including a pair of trip magnets in the trip loop, and an armature adapted to be attracted by either magnet to start the transmitter; a signal initiating means for each transmitter normally shunting the magnets and adapted to break the shunt and direct current from the trip loop through one magnet to the transmitter ground to start the transmitter and thereby short-circuit the trip magnets of more remote transmitters; means actuated by the transmitter at the beginning of transmission for removing its ground, and short circuiting its trip magnets, during and after transmission; and control means to disconnect said outer end from the ground and connect it to the ungrounded terminal of the source.

13. In combination, a trip loop; a single grounded current source therefor; code-signalimpulse transmitters each having a ground; said trip-loop passing through the transmitters and having one end connected to said source and the other end grounded; means separate from the trip loop for transmitting code signals from the transmitters; each transmitter including a trip magnet in the trip loop, and an armature adapted to be attracted by the magnet to start the transmitter; a signal initiating means for each transmitter adapted when in normal position for normally shunting the magnet and adapted when in actuated position to break the shunt and direct current from the trip loop through the magnet to the transmitter ground to start the transmitter and thereby short circuit the trip magnets or more remote transmitters; means actuated by the transmitter at the beginning of transmission and functioning in either position of the initiating means for removing its ground and directly short circuiting its trip magnets, during and after transmission, to prepare the trip loop for waiting stations; means for compelling a transmitting station to complete its code; and means for preventing trip loop current from starting other transmitter while a station is operating.

14. In combination, a source of current; a trip loop connected thereto; transmitters, each including a trip magnet adapted when sufficiently energized to cause the transmitter to operate from normal rest position; signal initiating means for shorting out the trip magnets of more remote transmitters and for causing current from the trip loop to pass through the trip magnet before the transmitter has started, thereby to start the transmitter; and means operated by the transmitter during transmitting, for reduc ing the current in the trip circuit to prevent release of another transmitter.

15. In combination, a grounded source of current; a transmitter circuit and a trip circuit each having one end grounded and the other connected to said source; means for disconnecting such grounds and connecting both ends of each circuit to said source; transmitters, each including a normally closed code switch, means for grounding the code switch, a pair of trip magnets disposed in series in the trip circuit, a ground connected to the connection between the magnets, either magnet being adapted when sufficiently energized to cause the transmitter, to operate; signal initiating means for causing current from the trip circuit to pass through either trip magnet to ground, thereby to start the transmitter; means set in operation by the transmitter during transmitting, for reducing the current in the-trip circuit enough to prevent release of another transmitter; and code signal receiving means operable by current in either end of the transmitter circuit.

16. In combination, a grounded source of current; a transmitter circuit and a trip circuit each having one end grounded and the other connected to said source; means for disconnecting such grounds and connecting both ends of each circuit to said source; transmitters, each including a pair of trip magnets in series in the trip circuit, a

ground connected to the connection between the magnets, either magnet being adapted when sufficiently energized to cause the transmitter to operate from normal rest position; and signal initiating means for causing current from the trip circuit to pass through either trip magnet to ground before the transmitter has started, there by to start the transmitter and short out more remote trip magnets.

1'7. In combination, a grounded current source; code-signal-impulse transmitters each having a ground; a trip-loop passing through the transmitters and having one end connected to said source and the other end grounded; means separate from the trip loop for transmitting code signals from the transmitters; each transmitter including a trip magnet in the trip loop, and an armature adapted to be attracted by the magnet, when sufiiciently energized, to start the transmitter; a control magnet in the trip loop between said ground and the transmitters; a signal initiating means for each transmitter adapted to direct current from the trip loop through the magnet to the transmitter ground to partially energize the trip magnet and toshort circuit the control magnet; means set in operation by the deenergization of the control magnet for increasing the current in the trip circuit, to sufiiciently energize the partially energized trip' magnet to start the transmitter.

RICHARD M. HOPKINS. 

